There have been conventionally known liquid crystal displays configured to carry out a desired display by sandwiching the upper and lower sides with polarizers, and by transmitting or not transmitting light in a vertical direction through a liquid crystal cell disposed such that the liquid crystal layer has a predetermined twisted angle (see Patent Document 1, for example). As an example of the above liquid crystal displays, there is known such a liquid crystal display 200 having a liquid crystal layer 240 as shown in FIGS. 10 and 11. For the sake of convenience, explanations will be given with the directions of arrow shown in FIGS. 10 and 11 as frontward, backward, leftward, rightward, upward and downward directions. The directors of the liquid crystal molecules constituting the liquid crystal layer 240 are the direction of an arrow 241 in the lower end portion, and the direction of an arrow 246 which turns the arrow 241 by 90 degrees clockwise in the frontward, backward, leftward, and rightward direction in the upper end portion as shown in FIG. 11, while the directors are gradually twisted to form a TN (Twisted Nematic) type in the intermediate portion.
Further, the liquid crystal layer 240 is sandwiched by alignment layers 232 on the upper and lower sides. Transparent electrodes 233 and 235 are provided on the upper and lower outsides of the alignment layers 232, and the transparent electrodes 235 are electrically connected to an AC power supply 236. The transparent electrodes 233 and 235 are sandwiched by substrates 231 on the upper and lower sides, and the substrates 231 and a seal material 234 seals the liquid crystal molecules of the liquid crystal layer 240. A liquid crystal cell 230 is thus constituted by these substrates 231, seal material 234, transparent electrodes 233 and 235, alignment layers 232, and liquid crystal layer 240. The liquid crystal cell 230 is sandwiched by polarizers 203 and 204 on the upper and lower sides, and arranged such that the transmission axis direction 203a of the polarizer 203 is parallel to the transmission axis direction 204a of the polarizer 204. A backlight 202 is disposed below the polarizer 203.
With respect to the liquid crystal display 200 of the above configuration, illumination light from the backlight 202 is irradiated to the liquid crystal cell 230, and an illumination light 202a changes the polarizing direction 90 degrees clockwise inside the liquid crystal cell 230 according to the twisted angle of the liquid crystal molecules inside the liquid crystal layer 240, and reaches the polarizer 204. At the time, as shown in FIG. 11, because the transmission axis direction 204a of the polarizer 204 is in a 90-degree turned position relation with the direction of the arrow 246, the illumination light 202a cannot be transmitted through the polarizer 204, and thereby that portion is darkly displayed.
On the other hand, if the AC power supply 236 applies a voltage to the transparent electrodes 235, the liquid crystal molecules inside the liquid crystal layer 240 will align with the major axis vertically directed. Therefore, an illumination light 202b travelling through the voltage-applied portion reaches the polarizer 204 without being twisted by the liquid crystal molecules inside the liquid crystal layer 240. That is, because the illumination light 202b reaches the polarizer 204 along the director of the arrow 241 without change, the illumination light 202b is transmitted through the polarizer 204, and thereby brightly displayed (negative mode). Thus, it is possible to brightly and darkly display a desired pattern (in black and white) by providing a plurality of transparent electrodes 235 for forming the desired patterns, and carrying out control of the voltage application from the AC power supply to each transparent electrode. Further, it is possible to configure a dark display of the desired pattern inside a bright background (i.e. positive mode) by turning the polarizer 204 by 90 degrees, for example, in the frontward, backward, leftward and rightward direction.
Patent Document 1: JP2006-235581 A
The above liquid crystal display 200 provides negative mode of brightly displaying a desired pattern inside a dark background. However, under bright usage environments surrounded by outside light such as natural sunlight and the like, the outside light is reflected on the background to cause the background to look bright, and thus the contrast becomes smaller between the desired pattern being brightly displayed and the background, thereby lowering the visibility of the desired pattern.
Further, because the liquid crystal molecules inside the liquid crystal layer 240 are uniaxial birefringent crystal having an optical axis in the major axis direction, if an oblique illumination light 202c is transmitted in the minor axis direction of the liquid crystal layer 240 or in an oblique direction, it would occur a retardation upon transmission through the liquid crystal cell 230 due to the influence of birefringence. Thereby, when the oblique illumination light 202c is obliquely transmitted through the above liquid crystal display 200, that is, when the liquid crystal display 200 is viewed at an angle, it gives rise to color shift due to the retardation in comparison with the illumination light 202b, that is, when the liquid crystal display 200 is viewed directly above.